Abstract Scope |
Selective laser melting of Al7075, a high-strength aluminum alloy is highly challenging because of its hot-cracking susceptibility. A comprehensive experimental-computational investigation has been carried out to understand the formation of solidification-cracking, porosity, and build surface quality and to predict optimum conditions for defect-free parts by varying laser power, scanning speed, baseplate heating, and re-melting. Detailed characterization and quantification of submicron-scale solidification cracks and porosities are carried out using high-resolution X-ray microtomography. We observed that conventional SLM processing results in crack formation because of insufficient liquid backfilling in between long columnar-dendritic grains formed towards build-direction, whereas a novel combination of re-melting and baseplate heating produces controlled solidification conditions which result in reduction of crack, porosity, and improvement in surface finish. Finally, the solidification path for all processing conditions is predicted with the help of high-fidelity multi-physics particle-scale SLM model. The model results are used for understanding defect formation and mitigation mechanisms. |